Electric Steering applications such as Electric Power Steering (EPS), four wheel steering e.g., Quadrasteer (Qsteer) Active Front Steer (AFS), Active Rear Steer (ARS) are used in vehicles to improve performance fuel economy and stability of the vehicle. Commonly, in such systems an electronic controller is configured to drive an electric motor to provide torque, speed or positioning control.
Electric steering systems often employ digital encoders for motor position feedback. Owing to their low cost and capability of operating at high temperature and in harsh environment, Hall type sensor based encoders are preferred in electric steering motor drive applications than those employing optical detection. Hall effect position sensors are, however, very limited in providing high resolution position and/or speed signals, often required for desirable performance of an electric steering system. Although, resolvers have traditionally been used to provide high precision position and speed information for servo drives, the cost of both the resolver itself and the associated electronics for interfacing a resolver with a digital motor controller have long prevented them from being used in the low cost automotive products. Advantageously, in the past few years, a variable reluctance resolver has been developed, which features a very simple, rugged structure and yet is cost competitive to Hall effect encoders. However, the additional cost of the associated electronics to interface a resolver to a microprocessor or digital controller still presents a significant impediment to commercial viability and the potential to replace the Hall encoders for automotive applications. Therefore, what is desired in the art is a means for interfacing a resolver with a digital motor controller or microprocessor without the expense of traditional electronic interfaces and conversion circuits.